When anti-spam feature is enabled firewall will create necessary access rules and NAT policies automatically. If any of the Anti-spam related default objects/services are used in custom rules , there will be some unusual issues.
One such issue is anti-spam rules gets auto disabled when firewall is rebooted. This article describes some best points to consider while adding custome rules related to mails with CASS enabled.
If the CASS service is not active, theSMTP (Anti-Spam Inbound Port)should never be used anywhere.
If you want to add any custom rules related to SMTP, alwayse use service object"SMTP(send EMail)"
If exchange server is using any group of service object with CASS enabled, ensureSMTP(send Email), port 25, SMTP (Anti-Spam Inbound Port)services are not part of it.